System Diagnosis - Except Electronically Controlled System

TROUBLESHOOTING
The AIR system is not completely noiseless. Under normal operating conditions, noise from the system increases as engine speed increases. To determine whether abnormal engine compartment noises are caused by the AIR system, operate engine with pump drive belt disconnected. If noise is eliminated, use the following checks to determine which system component is the cause for the complaint.
1. Excessive belt noise:
a. Inspect drive belt and replace or adjust as necessary.
b. Check for seized air pump.
2. Excessive pump noise; chirping, knocking, rumbling:
a. Check for loose air pump hoses and tighten or replace clamps as needed.
b. Check for leaking distribution hoses and replace as needed.
c. Check that air pump hoses are not contacting other engine components and align hoses as needed.
d. Check ACV or diverter valve operation and replace as needed.
e. Test check valves and replace as needed.
f. Loosen and retorque pump mounting bolts and check pump aligNment.
g. Check for damaged or seized air pump and replace as needed.
3. If air pump output is insufficient check the following:
a. Defective air flow control valve.
b. Defective check valves.
c. Clogged air distribution pipes or nozzles.
d. Defective pressure relief valve.
e. Defective air pump.
4. After fire in exhaust system:
a. Check fuel and ignition system operation and correct as needed.
b. Check air flow control valve operation and replace as needed.
c. Check vacuum hose routing to air flow and deceleration valves, if equipped, and correct as needed.
d. Check for defective vacuum switch in signal line to air flow control valve and replace as needed.
In general, a malfunction in the AIR system will not cause rough running, hesitation, lack of power or surging. However, several of these driveability complaints, along with reduced efficiency of the AIR system, can be caused by a restricted exhaust system. Refer to ``Catalytic Converters'' for the ``Exhaust System Check.''

AIR CONTROL VALVE TEST

1. Start engine and run until it reaches normal operating temperature.
2. Observe valve while accelerator pedal is fully depressed, then quickly released.
3. Valve should discharge air for approximately 5 seconds.
4. If valve discharges air for more than 5 seconds, valve is defective.

CHECK VALVE TEST

1. Disconnect hose and remove valve from manifold.
2. Blow through valve from both directions.
3. Air should flow from pump to manifold side, but no air should flow from manifold to pump side.
4. If check valve does not perform as outlined, replace valve.



DECELERATION & MIXTURE CONTROL VALVE TEST

Except 4-119 Engines

1. Remove air cleaner and plug air cleaner vacuum source fitting.
2. Connect tachometer to engine following manufacturer's instructions, start engine and set engine to run at specified curb idle speed.
3. Momentarily disconnect vacuum signal hose from valve while observing air flow through valve.
4. Engine idle speed should drop noticeably and air should flow through valve for at least 1 second.
5. If valve does not perform as outlined, check for leaks or restrictions in vacuum supply hoses.
6. If vacuum supply is satisfactory but valve does not perform as outlined, replace valve.